Yeah the case really limits in batterysize.You could keep the size down if you used a 900 mah 30c, that gives you a constant of 27 amps, so some wiggle room
I found this battery: E-Flite LiPo Battery 11.1V (EFLB8003SJ30) | Airplane Batteries | RC Planet
The 24A are close but enough.
Actually I searched for suitable batteries for 4 hours today. That's one of a few that fit the case.

